Spectrum of Acrolein

Abstract

IN connexion with measurements on the photo chemical decomposition of acrolein we have measured (Hilger E 315 spectrograph) its ultra-violet absorption spectrum. There are two distinct regions of absorption, one consisting of bands with no overlapping continuum, extending from c. 4000 A. to 2800 A, ; the other of continuous absorption beginning at c. 2300 A. and extending towards higher frequencies. The first region becomes continuous at pressures above c. 60 mm. These results agree essentially with the earlier work of Lüthy¹. The first region corresponds to absorption by the carbonyl group. Saturated ketones have also been found to give banded absorption below c. 2100 A., so that the second region found here might also involve absorption by the carbonyl group. On the other hand, some facts suggest that the continuous absorption is really to be attributed to a primary excitation of the C = C link. In consequence of the conjugated grouping this may be displaced towards the red as compared with that usually found.